WASHINGTON  Just hours before President Bush left
for Europe on Monday, he met with Sen. Joseph Biden, D-Del., the new chairman
of the Senate Foreign Relations Committee.

The meeting was mainly a courtesy call, but it underscored
a new reality for Bush: Even as the president tries to coax reluctant NATO allies
in Brussels Wednesday to endorse his goal of building a national missile defense,
he will face stiff resistance to his plan from a Senate that has fallen into
control of the Democrats. And Biden will be using his new power to lead the
opposition.

"I can think of no more important decision that I could
take part in," Biden said in a recent interview. "This is one of those things
worth losing an election over."

Together with new Senate Majority Leader Tom Daschle, D-S.D.,
and Armed Services Chairman Carl Levin, D-Mich., Biden could become a formidable
roadblock for Bush's missile-defense plan. By contrast, Sen. Jesse Helms, R-N.C.,
who had been Foreign Relations chairman, was a big booster of a missile-defense
program.

Bush has called for using U.S. air-, sea- and land-based
defenses to protect against missile attacks from hostile nations such as Iran
or North Korea. He has yet to spell out how such a system would work or what
it would cost. Critics say a broad system envisioned by Bush could cost into
the hundreds of billions of dollars.

When the administration makes a specific proposal, "you
can expect Joe Biden to go over it with a fine-tooth comb," says Joseph Cirincione,
director of the Non-Proliferation Project at the Carnegie Endowment for International
Peace, which is based in Washington.

Analysts say many European leaders, who fear a U.S. missile-defense
system would spark a new arms race, seem to have strengthened their resolve
to oppose the plan since last week's Democratic takeover of the Senate. On Capitol
Hill, meanwhile, sentiment is growing that Congress can't afford to finance
an expensive missile-defense program after passing a 10-year, $1.35 trillion
tax cut sought by Bush. Lawmakers have provided $55 billion since 1984 for research
and testing. The Bush administration wants to ramp up spending from $5 billion
this year to as much as $8 billion next year.

Biden, long a Democratic leader in foreign affairs, supports
continued research into missile-defense technology, and he says he might support
a scaled-down system but not Bush's ambitious plan.

"If you ask people where they are on national missile defense
... they say they are for it," Biden says. "When you ask them if they are for
a national missile defense that a lot of scientists say won't work, that support
starts to drops off a cliff. Or if you tell them it could cost tens of billions
if not hundreds of billions of dollars."

Political analysts say Biden's leading role in this debate
might play nicely into a presidential run in 2004, which Biden is considering,
according to his aides. "This is an issue you can use to draw a clear distinction
with the White House," says Jennifer Duffy, Senate editor for the Cook Political
Report.

But there also might be a political downside to opposing
a system that Bush argues will make America secure. Analysts say that a Democrat
who opposes missile defense risks being branded "soft" on military issues. What's
more, national missile defense isn't exactly a topic most Americans discuss
at the dinner table.

Some senior Democratic Senate aides don't relish the prospect
of a more visible Biden flirting with a race for the White House. He ran for
the 1988 Democratic nomination but quit after negative publicity over his admission
that he plagiarized passages of speeches given by a British politician, Neil
Kinnock. Biden is also known as one of the Senate's most long-winded orators.

Despite his detractors, Biden is in a position to make
life difficult for Bush on missile defense and other foreign policy matters:

 A Biden-led committee might block the confirmation
of Otto Reich, Bush's choice to head the State Department's Latin America bureau.
Reich has been criticized for overseeing a covert campaign to boost public support
for U.S. aid to Nicaraguan rebels during the Reagan administration.

 Biden will push the Bush administration to remain
committed to arms-control treaties, particularly the 1972 Anti-Ballistic Missile
Treaty, which bars most missile defense system. The president says the ABM Treaty
between the United States and Soviet Union is invalid and should be scrapped
because the Soviet Union no longer exists.

 Biden has taken a leading role in shaping U.S. policy
in the Balkans, and he says he will resist administration moves to pull U.S.
troops out of Bosnia-Herzegovina or Kosovo. Biden's first hearing as Foreign
Relations chairman Wednesday looks at the unrest in Macedonia and U.S. involvement
in the Balkan region.